Background & Management

Definition

 

Displacement of proximal femoral epiphysis in the immature hip

- due to imbalance of mechanical and endocrine factors 

 

Epidemiology

 

Age Peak Incidence : M 12-14; F 11-13; Slight downward trend due to earlier maturation of children

L hip > R

10 / 100 000

 

Bilateral SUFE

 

No endocrine abnormality

- 20% at time of of diagnosis

- another 20% during diagnosis

- up to 60% with long term follow up

 

Endocrine abnormality

- up to 75%

 

Risk Factors

 

Demographic Factors

- Increased Weight and Height (50% over 95th percentile weight; 50% over 97th percentile height); Average BMI 27  

- Race : Increased risk in Black pts (4X) ; Polynesian ; Hispanics

- Sex : Male 2.5 x risk

- Family History - 7 % risk to other family members

 

Hip Mechanical Factors - increased shear forces

- increased slope (at adolescence growth plate goes from horizontal to vertical position)

- increased retroversion Southwick angle > 14

- reduced neck shaft angle

 

Endocrinopathies

Imbalance of

- Testosterone - causes physeal fusion

- Growth hormone - causes physeal hypertrophy / weakens

 

Causes

- hypothyroidism

- hypopituitary

- acromegaly or growth hormone supplementation

- CRF/ Renal Osteodystrophy

 

Other

Connective Tissue Disorders - Marfan's / Downs / Ehlos Danlos

Chemo therapy / DXRT

 

Pathology

 

Widened hypertrophic zone 

- constitutes 60% of physeal width 

 

Abnormality at Hypertrophic & Proliferative Zones junction

- failure occurs here

- disordered chondrocyte columns

- decreased number of cells

- cells smaller

- increased number of dead and degenerative cells

 

Head remains in acetabulum via L. Teres

- neck displaces anterosuperior on physis and ER

- head slips posterior / inferior on neck

 

Classification

 

Chronological

 

Acute < 3/52 symptoms

Acute on Chronic 

Chronic >3/52

 

Morphological 

 

Southwick Slip angle

- Wayne Southwick ; 1st Chairmen of Orthopaedics at Yale University

- lateral X-ray  / frogs legs

- epiphyseal-shaft angle 

- angle of interest is the angle of the affected side subtracted from the normal contralateral side ; if contralateral SUFE then 12 degres as normal    

- <30° / 30- 50 / >50°

- mild / moderate / severe

 

Stability

 

Loder JBJS 1993

 

Stable 

- able to weight bear / 0% AVN

 

Unstable 

- unable to weight bear / AVN rates 10 - 60%

 

History

 

Overweight adolescent boy hip or knee pain; 30% present only with knee pain

 

Examination

 

Limps

Walk with ER (chronic) i.e increase in foot progression angle

Obligate abduction and external rotation with flexion

Limitation IR / Abduction

LLD (real and apparent)

 

X-ray

 

AP

 

SUFE AP

 

Trethowan Line / Kleins Line

- line along superior neck usually transects 20% head

- originally described as AP but can also be used as lateral

 

Widened physis

 

Inferomedial remodelling in chronic slip

 

Metaphyseal Blanch Sign of Steel

- Increased cresenteric density in the metaphysis due to overlapping of the metaphysis with the epiphysis

 

Capener's Sign

- the posterior acetabular margin normally cuts the medial corner of the metaphysis

- in a slip the whole of the metaphysis remains lateral to the acetabular margin

 

Frog Leg Laterals / Shoot through lateral

 

SUFE Lateral

 

Shoot through lateral

- best to avoid frog leg lateral as may displace slip

 

Posteriorly displaced & angulated

 

Measure Southwick Angle

- calculate severity of slip

- also estimates risk of slip of other side / looking for retroversion

 

Management

 

Aims

 

1.  Prevent further slip / obtain physis fusion

- 30% will continue untreated

 

2   Prevent deformity and OA

- MUA / ORIF / osteotomy

 

3.  Avoid complications 

 

Algorithm

 

Loder RT et al. What is the best evidence for treatment of slipped capital femoral epiphysis?

Journal of Pediatric Orthopaedics. 2012 Sept : 32 (Suppl 2) S158 - 65

 

Stable : Insitu Pinning current gold standard

 

Unstable : Two schools of thought

  1) < 24 hours old

- Consider treatment as a surgical emergency

- urgent reduction (gentle traction, flexion and internal rotation) +/- joint decompression

- probably results in lowest AVN rates (Petersen et al - refer below)

- alternatively consider discussion with tertiary paediatric referral centre

 

  2) > 24 hours

- Discuss with specialist paediatric centres

- possibility of surgical dislocation and realignment i.e. Modified Dunn Procedure

 

In Situ Pinning

 

Gold Standard (Techique refer below)

 

CT post operatively

- ensure no screw protrusion

 

TWB 6/52

 

Serial Xray

- ensure epiphysis doesn't grow off screw

- screw can break / can lose position

- observe til physis closes

- no indication to remove pin

 

Results

 

Weinstein et al JBJS Am 1991

- 40 year follow up of 155 hips

- some pinned in situ / some realigned / some reduced

- rates of OA / AVN / chondrolysis increased with severity of slip

- rates of OA / AVN / chondrolysis increased with reduction / realigned

- regardless of severity of slip, pinning in situ had best results with lowest complications

 

Closed Reduction Prior to Pinning

 

Disadvantage

 

Traditionally associated with higher risk AVN

 

Advantage

 

Theorectical

- may decrease AVN in severe, unstable hips

- prevent severe deformity / late OA

 

Indication

 

Acute & unstable < 24 hours

 

Results

 

Peterson et al J Paediatr Orthop 1997

- 91 cases of severe, acute, unstable slips

- 42 closed reduction < 24hrs AVN 7%

- 49 closed reduction > 24hrs AVN 20%

- hypothesised that had acute obstruction of epiphyseal vessels 

- timely decompression allows revascularisation

- treat an acute unstable slip as per a fracture

- these have up to 50% AVN rate anyway

- emergency operation

 

Chen et al J Paediatr Orthop 2009

- 30 acute, unstable slips

- 25 closed reductions and 5 open reductions with release hematoma

- 4 cases of AVN

 

Open Reduction Prior to Pinning

 

Indications

- severely displaced slips

 

Reasoning

- moderate or severe slips do poorly in long term

- best treatment is intra-capsular reduction or osteotomy

- risk AVN either way

- acute open reduction easier

- also decompress hip

 

Modified Dunn Procedure

 

Ziebarth et al. Capital realignment for moderate and severe SCFE using a modified dunn approach.

Clin Orthop Relat Res. 2009; 467(3): 704 - 16

- Ganz type transtrochanteric approach

- Z shaped capsulotomy to preserve superior vessel along neck, along anterior acetabulum and inferior neck

- capsule banana skinned off neck

- hip dislocated via adduction and external rotation and transection of the round ligament

- epiphysis taken off neck, still attached to capsule

- intraoperative monitoring of epiphyseal perfusion via 2mm hole drilled in the anterior neck or via insertion of ICP monitor into the epiphysis

- neck debrided to avoid tensioning of posterior vessels

- head replaced and pinned as per normal

 

Results

 

Sankar WN et al. The modified Dunn procedure for unstable slipped capital femoral epiphysis: a multicentre prospective.

JBJS (Am). 2013; 95:585- 91.

- 26% Rate of AVN

- 15% Revision of metalwork rates

- therefore capable of restoring anatomy but ongoing risk of AVN and metalwork complications.

 

Prophylactic Pinning

 

Issues

 

Can justify but may cause complications 

- i.e. chondrolysis, subtrochanteric fracture secondary to screw

 

Incidence bilateral slips

- unknown

- may be > 35%

- high incidence of asymptomatic and mild contralateral slips

 

Major indications

- young i.e < 10 years

- unreliable parents

- geographic isolation

- Secondary SUFE eg endocrinopathy

 

Technique of Pin in Situ

 

Set up

 

1.  Supine on radiolucent table

- very easy to set up

- much faster if pinning both sides / reduced set up

- theoretical risk of displacing slip / inadvertant manipulation

- lateral by flexing and full ER of hip / frog legs

 

2.  Traction Table

- easy to get AP and lateral

- need 2 set ups for bilateral pinning

- takes longer in this regard

 

Technique

 

Draw anterior and lateral lines

- get AP, draw line mark using radiopague ruler to centre of head

- get lateral, repeat

- intersection of points is incision site

 

Stab incision

- guide wire percutaneously to neck

- more anterior entry point on femoral neck required the more the epiphysis is displaced posteriorly

- more anterior entry point ensures less likely to start at a subtrochanteric position and risk stress fracture

- central in head on both views

- ensure don't penetrate head

- cannulated drill

- 6.5/ 7.0/ 7.3 screws

- 8-10 mm or 4-5 threads across physis

- do far and away screening / approach withdraw; circumferential screening

- this ensures screw is not in joint